Design and Development of Raman-Assisted Multibrillouin Stokes Laser Using Dispersion Compensating Fibre

• Main Author: Abdul Kadir @ Jaafar, Muhammad Zamzuri
• Format: Thesis
• Language: English; English
• Published: 2008
• Online Access: http://psasir.upm.edu.my/id/eprint/7304/1/FK_2008_89a.pdf; http://psasir.upm.edu.my/id/eprint/7304/

Application of multiwavelength sources in Radio over Fibre (RoF) technology has been interesting research works since a last few decades. In order to achieve this source, many techniques have been proposed, whether using a single technology such as Brillouin fibre laser, Raman fibre laser, and erbium doped fibre laser (EDFL) or hybrid technology such as Brillouin-erbium fibre laser (BEFL) and Brillouin- Raman fibre laser (BRFL). Even though these proposed designs have their own advantages, they have not been thoroughly studied in terms of Stokes optical signalto- noise ratio (S-OSNR), Stokes peak power (SPP), flattened SPP, Stokes linewidth (SLW), and Stokes line count (SLC). In this research work, multiwavelength BRFL is proposed which consists of two different configurations, namely ring-cavity and linear cavity. These designs are configured so that the laser oscillation is assisted by internal reflection (e.g. Rayleigh scattering) and external reflection (e.g. Fresnel reflection, mirror or FBG). They are pumped by the Raman pump source (RPS) having wavelength at 1455-nm or 1450- nm. The mediums used for Raman and Brillouin effects are a few lengths of dispersion compensating fibre (DCF) from different manufacturers. All the designed parameters are seriously taken care so that these two configurations are comparable. It is observed that when the RPP is increased from 400-mW to 800-mW, the ring and linear cavity show the wavelength-shift of 2.12-nm and 3.72-nm respectively. The red-shift is larger for the latter since the forward and backward-Raman Stokes spectrum is amplified twice as well as the RPP is reflected into the DCF to be a second pump source. When the RPP is above 1000-mW, Rayleigh scattering contributes to the peak-power discrepancy between the odd and even order Stokes line, and it is worse for the ringcavity. This issue is nearly addressed by the linear-cavity design whereby all the Stokes lines are guided to make complete oscillation with the assistance of standing wave and Rayleigh scattering. The 3-dB SLW discrepancy between odd and even order is also observed from the ring-cavity. However, regardless of the BPP values, the 3-dB SLW becomes comparable to each other when the RPP is 1000-mW and above. For the linear-cavity, they become comparable when the RPP is 230-mW. Relation between the S-OSNR and SLC is also studied. Both cavities show that as the SLC increases, the Stokes-OSNR decreases. However, multi-Stokes lines featured with flat amplitude and almost equal OSNR have been achieved with the linear-cavity just pumped by a single RPS. These spectra contain 360 Stokes lines with 18-dB OSNR.